IMPACT DES REJETS MINIERS SUR LA QUALITE PHYSICO-CHIMIQUE ET BIOLOGIQUE DES EAUX SOUTERRAINES D'UNE ZONE MINIERE DANS LA REGION DE MARRAKECH (MAROC) IMPACT OF MINING WASTES ON THE PHYSICOCHEMICAL AND BIOLOGICAL CHARACTERISTICS OF GROUNDWATER IN A MINING A

摘要

Metal sulphide tailings represent a potential risk basically for the environment and particularly for water resources, because of their natural oxidisability which leads to the production of acideutral mine drainage. The prospected site close to Marrakech includes zinc, lead and copper sulphide deposits.This site is located in an agricultural area where ground water is used both for irrigation and drinking. Eco-toxicological investigations have been undertaken in order to asses the tailings impact on water quality in nearby wells. These investigations include physico-chemical characterization of the groundwaters as well as faunistic population determination. As compared to standard wells, waters from the wells located downstream of the mining site, have high electrical conductivities and high major ions contents, which can reach : 755 mg l~(-1) in SO_4~(2-), 1670 mg l~(-1) in Ca~(2+), 528 mg l~(-1) in Mg~(2+), 2289 mg l~(-1) in Na~+ and 14981 mg l~(-1) in Cl~-. The fauna distribution analysis carried out around the studied wells shows qualitative and quantitative differences according to the flow gradient of the groundwaters. Areas located upstream of the mine tailings site are richer in stygobite species (Type and quantity) than those located downstream or close to it. It is likely that these biological differences are due to water quality alteration induced by the mining activity.